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Nowadays, the seismic performance-based design of structures has been widely noticed by the engineering community. So, different methods for performance-based design have been presented by different researchers. This attitude has been included in the design code and regulations for seismic design of new buildings and retrofit of existing buildings. The FEMA P-58 performance-based design method presented by the Pacific Earthquake Engineering Research (PEER) can quantify the consequences related to the seismic response of buildings. Therefore, using this method, the seismic performance of buildings can be directly evaluated. In addition, this performance-based design method can define simpler criteria such as repair cost, repair time, and casualties for seismic evaluation and decision-making process. The method is based on considering different sources of uncertainty in earthquake input and its intensity, structural response, associated damage, and repair cost, using the concepts of conditional probability and total probability theorem. In this method, the building is designed in such a way that it meets the expected and predetermined performance level in a specific level of seismic excitation. Since the performance levels of the building are determined based on the amount of damage caused to structural and non-structural members, one of the practical and effective ways to evaluate performance is to estimate the building repair cost. In the approach presented in FEMA P-58, the repair cost is defined in a probabilistic approach, as the cost needed to restore the damaged parts to their original state in the form of expected annual loss. In this research, first, three 4-, 12-, and 20-story office buildings with the lateral force resisting system of reinforced concrete special moment frames were selected in a high seismic risk area. Then, the nonlinear model of structures was provided in OpenSEES software. In order to reduce the computational cost and analysis time, the single-bay Substitute Frame model was used to simplify the multi-bay reinforced concrete moment frames. All four structures were subjected to Incremental Dynamic Analysis (IDA) for 30 earthquake records. A probabilistic relationship between the spectral acceleration of the earthquake and the main damage parameter (i.e. the inter-story drift), as well as the collapse fragility curve, was obtained. Then, the repair cost including the cost of repairing structural members as well as beams and columns, the cost of repairing non-structural members as well as partition and curtain walls, and the cost of replacing collapsed structures was calculated as expected annual loss. The results show that the repair costs at the Design-Based Earthquake (DBE) for 4-, 12-, and 20-story buildings are 3%, 2.5%, and 10% of the building replacement cost and at Maximum Credible Earthquake (MCE) are 22%, 23%, and 38% of the building replacement cost, respectively. In addition, in short buildings, most of the cost is caused by repairing structural and non-structural members, and in tall buildings, most of the cost is caused by replacing collapsed or severely damaged structures. Considering two nonstructural elements (i.e. partition and curtain walls) in repair cost, the analysis results show that the cost of repairing structural elements is more than the cost of repairing non-structural elements.

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A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper.

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Most previous laboratory studies of local scour at bridge abutments were performed in rectangular channels in which the distributions of flow velocity and bed shear stress were considered uniform in the transverse direction. In reality however, bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress distributions are directly affected by the lateral momentum transfer. The influence of channel geometry and lateral momentum transfer in compound flow field on scouring phenomenon, however, has not been fully investigated and understood as yet. This paper presents the results of an experimental study performed to investigate the impact of both sediment size and lateral momentum transfer on local scour at abutments terminating in the floodplain of a compound channel. It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (yalH<0.3), estimates of maximum local scour depth are increased by up to 30% . In relation to the sediment size, earlier studies of scouring around circular bridge piers proposed a limit for the relative size of sediment (pier diameter/median size of bed material) beyond which the sediment size has no effect on the equilibrium scour depth (Ettema, 1980; Chiew, 1984). The results of the current laboratory studies, however, indicated that the limit established for circular bridge piers might not be appropriate for the abutment case installed in the floodplain zones; further studies are required to draw a more general conclusion regarding the effects of relative grain size in the abutment case.

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In this paper, a generalized method for accurate full-wave analysis of shielded MIC's and the three-layer microstrip structure enclosed in a rectangular cavity based on Mixed Potential Integral Equation (MPIE) derived in real space have been developed. Method of moments (MoM) with Galerkin technique has been used for the solution of the integral equation to obtain the surface electric currents distribution on the conductors. An accurate de-embedding procedure for the characterizing electric currents distribution and extracting S parameters based on pencil of matrix technique are employed. A new numerical technique for fast convergence of the double infinite series expansion of the MoM solution has been considered. A computer program implementing the analysis has been written in Fortran on a personal computer. Several types of microstrip discontinuities such as Open-end, bend, collinear Broadside Coupled Line (BCL) and crossover is analyzed and numerical results are presented and compared with both previously published data and the results found by HP-HFSS software.

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  Citrus, especially orange, are of great important among agricultural products in the world. In this study thin-layer drying of orange (var. Thompson) was modeled using artificial neural network (ANN). An experimental dryer was used. Thin-layer of orange slices at five air temperatures (40, 50, 60, 70 & 80 ºC), three air velocities (0.5, 1 & 2 m/s) and three thicknesses (2, 4 & 6 mm) were artificially dried. Initial M.C. during all experiments was between 5.4 to 5.7 (g/g) (d.b.). Mass of samples were recorded and saved every 5 sec. using a digital balance connected to a PC. MLP with momentum and LM were used to train the ANNS. In order to develop ANN's models, temperatures, air velocity and time are used as input vectors and moisture ration as the output. Results showed a 3-6-1 topology for thickness of 2 mm, 3-7-1 topology for thickness of 4 mm and 3-5-1 topology for thickness of 6 mm, with LM algorithm and TANSIG activation function were able to predict moisture ratio withof  0.99906, 0.99919 and 0.99930 respectively. The corresponding MSE for this topology were 0.00013, 0.00012 and 0.00009 respectively.

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Casual relationship between financial developments and economic growth is one of the striking empirical macroeconomic relationships. Following the development of financial issues, our attention turns from economic growth to another issue of economic welfare. In this study, we try to examine the relationship between financial developments, economic growth, poverty and inequality in OPEC countries. The simulation of the models and statistical inferences, in this study, are based on the static and dynamic panel data approach. The empirical models are estimated by using GMM estimators, fixed effects and random effects using the data between 1990 and 2004. The results of this study show that financial developments through its effect on economic growth can mainly contribute poverty alleviation and inequality reduction in these countries.

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Abstract Low height beams in concrete moment frames, decrease the ability of beams in controlling lateral displacement of buildings. Because of that, in the sixth subject from Iranian Regulations of Buildings and its following, in the 3rd edition of Standard 2800, the height of buildings with low height beams has been limited to 3 floors or 10 meters. According to that, in this study, concrete buildings with different amount of stories and moment frames, with medium ductility and the height of beams in 30 centimeters, have been analyzed (with linear equivalent static and spectral dynamic analysis Methods)and designed on the basis of seismic principles in the 2nd and 3rd edition of Standard 2800. Finally, studies continued with nonlinear static analysis and the performance point of structures determined (with capacity spectrum and displacement coefficient methods) in 4 levels of different seismic risks. Studies show that only one or two story buildings that designed with 2nd edition of Standard 2800 have enough safety in design base earthquake level (DBE) and also higher buildings, should go under rehabilitation.

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Abstract The moment connections sustained by many steel buildings were damaged during the recent earthquakes due to brittle fractures in the special moment resistant frames. Previous studies showed that although the top beam flange resisted due to the interaction of concrete slab, many damages are created because of weld cracking between the bottom beam flange and the column flange. Different methods of retrofit and rehabilitation could be used to prevent weld cracking and brittle fracture of the joints. The reduction of the bottom flanges of steel beams near the beam-column joints in the special moment resistant frames is currently an acceptable alteration of a connection because the top flange is located in the concrete slab and removing of concrete slab has financial and technical problems. RBS connection is one of the different kinds of Post-Northridge connections in which by cutting some parts of the flange near the end of the beam (where the possibility of making plastic hinges is high), the plastic hinge moves by the side of the column into the area within the beam. By using this method, the connection is altered from the special moment frame into a more ductile connection that has more ability to endure in plastic rotation, and generally ductility increases. The ductility of the panel zone is one of the parameters, which undoubtedly affects the manner of the yield of beams with RBS connection. Our findings in this work showed that new method causes the beam plastic rotation to increase by 30%. In addition, the applied force at the panel zone (according to the capacity of panel zone) is decreased. When compared to the frames without cuts, these reductions result in a 52% decrease in the plastic rotation of the panel zone, we also investigated the amount of dissipated energy by beams in the conditions before and after retrofitting. ANSYS software was used to study and analyze the non-linear behavior in the area of connections.

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Abstract Studying the response details of steel moment connections is very important due to the role of connections in moment resisting frames. The aims of this research were: i) to study the damage indices of steel material including: Pressure Index, Mises Index, Equivalent Plastic Strain Index, Triaxiality Index, and Rupture Index and ii) to compare these indices at connections of steel moment frames under earthquake loads. To achieve this, time history nonlinear dynamic analysis is performed using selected earthquake records on 2D model of special steel frame with ten storey and one bay to determine maximum rotations of connections. Then, damages indices of the selected connections under maximum rotation of records are investigated with selecting two types of moment connections. The results indicate that damage indices are dependent on type of connection, location of surveying, and rotations caused by earthquake movements. This dependency is very considerable for Equivalent Plastic Strain Index and Ruptureindices

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The inertial forces and moments, due to the motion of robotic arms installed on a mobile base, lead to reaction forces on the moving base which may cause its unexpected motion. In this article, a method of designing a path of motion in the Cartesian space between the initial and final positions is presented which guarantees no reaction on the moving base. To this end, developing the system dynamics model, the moment equations are derived. Based on the conservation of momentum in the absence of any external force and moments, the angular motion due to the motion of robotic arms is solved. Then, based on the definition of reaction null-space map for dynamic coupling matrix, the joint speeds are projected to the reaction null-space, to obtain the joint speeds in this space. Next, using numerical integration of the obtained joint rates, the motion in the joint space with no reaction on the base is obtained. Therefore, motion of robotic arms according to these joint specifications, the total momentum of the system remains zero, and due to no reaction forces applied on the moving base, its position and attitude remains unchanged.

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This paper presents the results of a study on the radiation characteristics of a plasma triangular antenna in the VHF band (30-300MHz) applying the method of moment. Deriving the current distribution of the antenna, it shows the relationship between radiation characteristics of the plasma antenna and the plasma parameters. Both theoretical and numerical results indicate that if the plasma frequency is sufficiently higher than the operating frequency and the collision frequency is correspondingly low, the radiation treatment of the plasma antenna will be close to a metal one. Also the consequence of simulations reveals the proposed plasma antenna has better peak gain than the conventional plasma column on the operating band. The results of the current study are checked by using full wave HFSS simulator.    

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Progressive collapse of buildings has raised questions on adequacy of the existing regulations to prevent local and, in turn, global collapses. The present study mostly focuses on the performance of welded moment connections against progressive collapse. The performance of moment connections suggested in the FEMA 350, which are proper for seismic forces, Welded Flange Plate (WFP), Reduced Beam Seaction (RBS), Welded Unreinforced Flange- Welded Web (WUF-W) and Free Flange (FF), has been studied. The models used include non-linear behavior of materials and geometrical nonlinear behavior. The behavior of steel materials used in the structure is the true behavior of steel was stress-strain, which has been considered in the model completely. The nonlinear stress-strain behavior of steel selected for modeling the real behavior of beam and column members in the structure. The material properties of all steel components were modeled using elastic-plastic material model from ABAQUS. For connection region porous material plasticity was used. The diagram of vertical force against vertical displacement for each connection was drawn, and the state of each connection failure was investigated. Making the large scale experimental models to study the progressive collapse of structures seems too difficult. Using finite element models to study the behavior of structures are relatively appropriate option with regard to time and cost. In all of the numerical models, shell (S4) element has been used to simulate the beams, columns and connections. This is a four-node element, which contains four integration points on the element. During the calculations, full integration method with more precision was used. For analysis of the models, dynamic explicit method was used. This method is suitable to analyze the models with more members having nonlinear characteristics of materials and large deformations. In this method, the central difference integrating is used to solve the dynamic equations. In every time step, this method performs simpler than other methods in solving dynamic equations since there is no need to inverse stiffness matrix in any time stage. The used numerical method has compared using the laboratorial results, which have tested in 2010 by NIST. The analytical results showed a good agreement with laboratory models. The results of numerical analyses illustrated that RBS connection has less strength in comparison with other connections and this connection reaches maximum vertical displacement with less force. Performance of FF and WUF-W connections is similar to each other. These connections more resistant in comparison with RBS. WFP connection is more resistant as compared with the WUF-W, FF and RBS connections against the failure of the column. Failure load in WFPconnection is twice of other connection, and according to the analytical results, this connection is suitable for HLOP structures. In all connections, rotation capacity corresponding to collapse prevention against column removal scenario is about twice of the accepted criteria that FEMA 350 has suggested for seismic loads.

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The design of the structural supports has always been practically important in engineering applications. In addition to holding a structure properly, supports can also be utilized to improve the structural performances. In this study, by using modified finite element method (MFEM) and Imperialist Competitive Algorithm (ICA), the maximum of bending moment was minimized. In this paper both elastic and rigid supports are taken into account. As compared to other design optimization methods, ICA is robust, more efficient, and requiring fewer number of function evaluations, while leading to better quality of results. Appling the modified finite element method not only reduces computational cost and increases convergence rate, but also reach the global optimum position of supports. Three classical examples are given to demonstrate the validity and capability of the proposed optimization procedure for finding the global support positions. Results show that support position optimization by using present method, can reduce the maximal moment significantly, and deserves more investigation.

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Numerical simulation of turbulent flow and heat transfer in film cooling from a cylindrical hole in three-dimensional case is considered. For this purpose, turbulent heat flux term of energy equation is usually modeled by simple eddy diffusivity model with constant turbulent Prandtl number, while experimental and numerical researches show that the prescribed constant value of turbulent Prandtl number is far from reality. In the present study, second moment closure (SMC) models with wall-reflection term is applied for modeling the turbulent flow and heat transfer in film cooling flow. Comparison between the numerical and experimental results show that the explicit algebraic second moment closure models have more ability to better prediction of temperature field in film cooling. In addition, turbulent Prandtl number distribution for film cooling has been investigated. The range of this parameter for the desired geometry has been identified from 0.1 to 0.95 in the near of injection hole to far from it respectively. Finally, in order to enhance the capability of simple eddy diffusivity model in simulating film cooling heat transfer, the value of 0.7 has been proposed for turbulent Prandtl number instead of the common value of 0.85.

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In this paper a method for online identification of satellite moment of inertia tensor parameters based on recursive least squares method, is presented. It is assumed that the satellite actuators are three orthogonal reaction wheels. Dynamic equations of the satellite are extracted in a special manner. The only available sensor is a three axes rate gyro which measures the angular velocity of satellite in the body coordinate system. Due to existence of noise in this sensor, the regressor matrix used in least squares method, changes stochastically. So in this case, the classic least squares method is not useful, and it cannot converge. For solving this problem, a modified least squares method with robust scheme is presented and its stability is proved using Lyapunov stability theory. The presented method can be used online in presence of measurement noise and other sensor imperfections. Simulation results have shown that this method can identify inertia parameters of the satellite with less than 3 percent error comparing to real parameters before and after changes.

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The moment-curvature envelope describes the changes in the force capacity with deformation during a nonlinear analysis. Therefore, the moment-curvature envelopes for columns, beams and shear walls form an essential part of the analysis. The program IDARC now provides an option for users to input their own cross-section properties directly, and the moment-curvature is computed internally. Since IDARC is most practical and well-known software in damage analysis and the value of Park damage index depends strongly on the ultimate curvature, truth of IDARC's results in section analysis is so highlighted. In IDARC, the moment-curvature analysis is carried out on the cross-section by dividing the concrete area into a number of strips or fibers. The section is subjected to increments of curvature and the strain distribution is obtained from compatibility and equilibrium considerations. In this study, the results of IDARC and OpenSees softwares in determination of moment-curvature curve and ultimate curvature of beams are evaluated. For assessment of the software's responses, there have been used of the experimental results for 9 reinforced concrete beams with different section properties. The moment-curvature analyses of these beams have been done by use of IDARC, OpenSees and finally the code that has been written in this study. Comparison of the results shows significant differences between the IDARC's results and other results. In order to control the accuracy of the analytical results two items have been checked, firstly, the strain of the last compressive concrete fiber in ultimate curvature and secondly, satisfying the equilibrium equations of section during the moment-curvature curve path. This study presents some cases that the axial equilibrium doesn't satisfy in the moment-curvature obtained by IDARC. Also, IDARC doesn't make attention to the ultimate strain of concrete when calculates the ultimate curvature. This result means that the damage index has been calculated by IDARC is not reliable when software accomplishes section analysis. Afterward, the used algorithm in IDARC for moment-curvature analysis has been revised and by proposing the modified algorithm a code has been written that can apply Chang&Mander and Kent&Park stress-strain concrete models. The effect of confinement on the concrete behavior has been applied based on Mander, Priestley and Park model and also based on Kent&Park model for each beam according to its transverse reinforcement. The results of the proposed algorithm conform exactly to OpenSees results. Although this results doesn't match exactly with experimental results, but the general form of moment-curvature curves are similar to somewhat that has been obtained in experiments. The main reason of this difference relates to the value assigned to the ultimate compressive strain of concrete. Since the Park model for estimate of ultimate compressive strain of concrete has been applied, and the efficiency of that is not to the point of this study, the mentioned difference is acceptable.

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Flood frequency analysis is faced with the problem of data and information limitation in arid and semi-arid regions. Particularly in these regions, the length of records is usually too short to ensure reliable quantile estimates. More than 75% of Iran is located in arid and semi-arid regions and despite the low annual precipitation, often large floods occur. One way to provide more information is to use many records from a region with similar flood behaviour, rather than only at-site data. This research is aimed to delineate homogeneous regions in the study area for further hydrological studies. Estimating regionalized parameters and identification of the best-fit distributions are the other specific objectives of the research. Several watershed attributes in relation to flood were characterized, among which the main characteristics were found by factor analysis. Later, preliminary identification of homogeneous regions was carried out using cluster analysis and region-of-influence approaches. The homogeneity test was done by H-statistic, a testing method based on L-moments. The results of this test showed that a subdivision of selected watersheds into homogenous groups is necessary. Therefore, three homogenous regions were formed. The Z-statistic based on L-moments and L-moment ratio diagrams were applied for identification of the best-fit distribution in each homogenous region. In the regionalization procedure five three-parameter distributions i.e. Generalized Logistic (GLO), Generalized Extreme Value (GEV), Generalized Pareto (GPA), three-parameter Lognormal (LN3), and Pearson type III (PE3) were fitted to the three homogeneous regions and the best-fit distributions were identified using L-moments approach. The results of goodness-of-fit analysis for the three regions indicates that the GEV, LN3 for the regions (1) and (2), and GLO and GEV distributions for the region (3) give acceptably close fits to the regional average L-moments. In general, the GEV distribution could be adopted as the appropriate distribution for the study area.

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In this paper, three-dimensional boundary layer flows on wind turbine blades as well as separation event have been studied. At first, boundary layer and three-dimensional momentum integral equations were obtained for incompressible flow considering rotation effects. Next, the effects of pitch angle and the angle between the flow direction and rotation vector on the Coriolis terms were applied using geometry factor definition and Blade Element Momentum (BEM) theory. Then, the integral parameters and effective geometry factors on separation positions and stall structure were investigated for a rotating blade. The obtained results show that rotational ratio, aspect ratio and radial position are three basic parameters for separation occurrence and separation and stall can be delayed via controlling them. Moreover, the results show that the area near the root is strongly influenced by rotational effects. In addition, it is concluded that the centrifugal pumping due to rotation decreases the boundary layer thickness and delays separation especially in the near root region and increases the blade aerodynamic coefficients.

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Box-columns are suitable members for structures with moment frames in two directions but performing the internal continuity plate in them causes some practical troubles. Details of the new proposal to alleviate this problem in box-columns is CONXL connection. This connection includes a set of Collar Flange Top (CFT), Collar Flange Bottom (CFB), Collar Corner Top (CCT), Collar Corner Bottom (CCB) and when the depth of the beams is more than 460 mm, Collar Corner Middle (CCM), Collar Web Extension (CWX) (only in the face of beam to column connection) and also a set of diagonal pre-tensioned high strength bolts (45 degrees angle), which collectively make up CONXL node. The bolts and collars performance make up a rigid diaphragm around the column. All collar flanges top and bottom are connected to the beam by means of groove welding with complete joint penetration, and the connection of collar web extension to the beams and that of collars corner to the column walls is made by fillet weld; collar corners are connected to each other through groove weld in factory and the pieces are just assembled in worksite. The objectives of presenting these details are industrializing, removing weld in workplace, removing continuity plate, enhancing quality, speeding up the construction, and simplifying the inspection. Through the distribution of force among collar systems, forces are transmitted from beams to the columns. The aim of this study is to numerically study the seismic behavior of CONXL connection without filler concrete of columns and to reduce the number of collar bolts with different arrangements. In order to reach this purpose, the numerical results of specimens; RBS and Kaiser bolted bracket (KBB) connection are compared to experimental results to verify the modeling and analyzing and good agreement is observed between numerical and experimental data. Afterward nine specimens of CONXL moment connections in box-columns not filled with concrete whit axial force in single, planer and bi-axial loading conditions with different arrangement of bolts are studied and their performances are evaluated. Results showed that seismic behavior of specimens with beam section depths equal or less than W30 series under cyclic loading, even with reducing the number of bolts to 16 numbers, is suitable in the over 0.04 radian rotations. Also, use of 16 numbers of bolts in connections with W30 series of beams, when it would be appropriate that use for corner connections (Single sided loading), and the specifications of ASTM-A36 for beams material to be used. Also, whatever the position of bolts to be outer than in collar flanges, axial strain in the bolts shank is bigger and its slip is less. The optimal position of the bolts is near the middle of the collar flanges. The results also showed that seismic behavior of all specimens with columns without concrete filling is appropriate and the column will remain without any remarkable local buckling in over 0.04 radian inter-story drift angle.

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In this article, a novel intelligent online tip-over avoidance algorithm is presented considering the interactions between the mobile base and manipulator arm. To this end, the newly suggested dynamic stability margin measure named Moment-Height-Stability (MHS) is adopted. Additionally, a function representing the increment of postural stability margin metric is defined based on MHS. The system dynamic equilibrium is then enhanced using a fuzzy logic approach. The response of the suggested method of this paper is compared with that of a previously Force-Angle based proposed one considering a planar mobile manipulator. First the dynamics of the robot is derived using Newton-Euler method via MAPLE 16 and it is verified through the model provided in SimMechanics toolbox of Simulink. The efficiency of the suggested method is illustrated in comparison to the previous one on a destabilizing robot path. Besides, the performance of proposed method of the present study is investigated in the presence of external disturbances. The obtained simulation results reveal the effectiveness of the performance of the suggested technique for stability improvement of wheeled mobile manipulators once encountering unexpected disturbing situations.